Which of the following is an essential step in antigen recognition during the immune response?

Explanation: Passive immunity is acquired when preformed antibodies are transferred to an individual, providing immediate but temporary protection against a specific pathogen. This can occur naturally from a mother to her newborn or artificially through administration of specific antibodies.

Incorrect choices:

a. Active immunity is acquired when the body's immune system is exposed to a pathogen and produces an immune response to provide protection against future infections.

c. Natural immunity refers to immunity that is acquired through natural exposure to a pathogen, either through infection or vaccination.

d. Herd immunity is the indirect protection that occurs when a large percentage of a population becomes immune to a disease, either through vaccination or previous infection, reducing the likelihood of transmission to susceptible individuals.

Explanation: Antigen recognition during the immune response occurs when antigens bind to specific receptors on immune cells, such as B cell receptors, T cell receptors, or antibodies. This binding is a critical step that triggers the activation of the immune response against the invading pathogen or foreign substance.

Incorrect choices:

a. Activation of regulatory T cells is important for controlling and regulating the immune response but is not directly related to the antigen recognition process.

b. Production of histamines by mast cells is involved in the inflammatory response, but it is not a direct step in the antigen recognition process.

d. Neutrophils are a type of white blood cell involved in the innate immune response. They do not release antibodies, as that function is primarily carried out by B cells and plasma cells.